Abstract: This study examines the efficiency and effectiveness of public evacuations of 1,000 or more people, in response to natural disasters, technological hazards, and malevolent acts, occurring in the United States between January 1, 1990, and June 30, 2003. A universe of 230 evacuation incidents was identified and a subset of 50 incidents was selected for case study analysis. Case study selection was based on a profiling and ranking scheme designed to identify evacuation incidents of sufficient complexity to challenge the local and regional emergency response capabilities. Case study analysis included completion of a detailed question survey for each incident. Advanced statistical methods, including regression analyses and correlation analyses, were used to identify factors contributing to evacuation efficiency. The regression analyses identified that community familiarity with alerting methods and door-to-door notification were statistically significant for a more efficient evacuation. The following factors were statistically significant for a less efficient evacuation: traffic accidents, number of deaths from the hazard, number of injuries caused by the evacuation, people spontaneously evacuating before being told to do so, people refusing to evacuate, and looting or vandalism. In addition, interviewees stated that the following contributed to the efficiency and effectiveness of their evacuation: a high level of cooperation among agencies, use of multiple forms of emergency communications, community familiarity with alerting methods, community cooperation, and well-trained emergency responders. All 50 evacuation cases studied safely evacuated people from the area, saved lives, and reduced the potential number of injuries from the hazard.